1. Field of the Invention
This invention relates to a stitching device or sewing apparatus for sewing along the perimeter of a circular or arcuate article and more particularly to an apparatus for sewing a pair of circular sheets together to form a restraint cushion or airbag.
2. Description of the Related Art
Feeding mechanisms for stitching or edging articles having a circular or arcuate configuration are known. For example, the U.S. Pat. Nos. of Lutz, 1,864,452 and 1,864,453, and of Smith, 4,240,366, disclose such mechanisms for sewing disc-shaped articles such as powder puffs, cushions or the like. Mechanisms of the type disclosed including feeding apparatus for positively directing the article to be stitched so that it turns about a fixed center and for holding the article in a manner which permits the article to be fed step by step about the center. For example, in the smith patent, a work station is adapted for receiving and maintaining a pair of superimposed sheets of fabric in position so as to allow the sheets to have the outer periphery thereof sewn together. The apparatus disclosed therein has a circular cover that cooperates with a similarly shaped rotatable table for clamping a pair of circular sheets of fabric in fixed relative positions with the peripheral portion of the sheets extending radially outwardly beyond the table so as to allow the sheets to be sewn together.
The device according to the prior art may be effective for sewing disc shaped articles at a relatively fast speed and to provide a relatively high degree of automation in sewing circular products as disclosed therein.
However, problems were encountered in attempting to sew large, circular layers of cloth or fabric for an airbag, i.e., the passive restraints that are now being installed in automobiles for protection of the passengers in the event of a collision. In stitching the large circular layers of cloth, problems of drag associated with the radially outwardly extending portions of cloth and difficulty in obtaining a smooth feed into a conventional stitching mechanism or sewing machine were encountered.
It should be understood that the demands of the commercial market require a relatively high degree of automation, a capability to sew products at a relatively high speed, with consistent and reproducible results and freedom from misfed or improperly stitched products. Accordingly, Applicant has invented an improved device which is applicable for stitching the circumference of airbags or the like.